Charge control resins have been used to give electric charges to toners, among which the negatively chargeable charge control resins which are colorless, white or pale-colored that are applicable for color toners include copolymers of a sulfonate group-containing acrylamide monomer and a vinyl monomer, a polycondensed product obtained by polycondensation reaction of a phenol and an aldehyde, and calixarene compounds, and the like. However, a further improvement in triboelectric chargeability has been desired for the toner in which the above-mentioned polycondensed product is used.
On the other hand, for example, JP-A-2002-40717 discloses a technique in which a charge control resin is present in the form of fine particles having specified length and width, by controlling the state of phase separation of the charge control resin using a resin binder containing a specified amount of a tetrahydrofuran (THF)-insoluble component, for the purposes of being free from background fog in any of low-humidity environment to high-humidity environment, showing excellent developability, and satisfying both the low-temperature fixing ability and the high-temperature offset resistance.
In addition, JP-A-2003-280266 discloses a toner containing at least a colorant and a calixarene compound as a charge control agent, obtained by dissolving a toner composition containing a modified polyester resin capable of forming a urea bond as a resin binder in an organic solvent, subjecting the solution to a poly-addition reaction in an aqueous medium to give a dispersion, removing the solvent of this dispersion, and washing the residue, for the purpose of obtaining a toner in which a charge control agent is homogeneously dispersed in the toner particles, thereby giving a stable triboelectric chargeability over a long period of time. Further, JP-A-2003-280266 discloses that a resin binder and a charge control agent are previously kneaded, whereby giving a state in which the resin binder and the charge control agent are initially sufficiently adhered to each other, thereby providing a state in which the dispersion is effectively carried out; consequently, the charge control agent is excellently dispersed in the resin binder, so that the dispersion diameter of the charge control agent becomes small, thereby giving excellent triboelectric properties, and that a resin binder, a charge control agent, and a solvent are mixed with a blender such as a Henschel mixer, upon previously kneading the resin binder and the charge control agent, and the resulting mixture is kneaded at a temperature lower than a melting temperature of the resin binder, with a kneader such as a twin roller or triple roller kneader to give a sample.
On the other hand, as a technique of pulverizing a charge control agent, JP-A-2006-154026 discloses a toner for electrostatic development containing a fine quaternary ammonium salt compound adjusted to a specified BET specific surface area by wet pulverization, for the purpose of sufficiently having charge control effects such as excellent triboelectric stability and triboelectric retainability even with a small amount of use.